Conventional Electromagnetically moving devices are used for switches or breakers each provided with a stationary contact and a movable contact, by which, when their turn-on coil is energized and excited, the movable contact is turned on and then the contact is retained by a magnetic force of their permanent magnet. Meanwhile, the opening operation is carried out in such a manner that their opening coil is energized and excited in a direction counteracting the attraction force of the permanent magnet, so that the contact is separated off due to a repulsive force of an energy-storing spring. Since the electromagnetically moving device is so structured as described above, when the electro-magnetically moving device fails, there is a likelihood that the breaker or its circuit is damaged, thus causing a power failure or the like. Accordingly, there is a demand for techniques to constantly recognize the operation status of the electromagnetically moving device. Main factors that may cause changes in behavior of the electromagnetically moving device, include: spring load; contact abrasion; movable-part friction; voltage drop in a power source for energizing a drive coil (capacity drop in a capacitor); and the like. Monitoring these changes makes it possible to prevent a failure of the breaker or the switch from occurring, and further, if a spot at which an abnormality is exhibited can be determined, an effect of saving effort in maintenance is promising.
It is easily conceivable to install a stroke sensor as a means for recognizing the status of the electromagnetically moving device; however, this can not avoid enlargement and cost increase of the device. Thus, with respect to a method without using a stroke sensor, there is proposed an electromagnet-operation monitoring device as disclosed in, for example, Patent Document 1. In the electromagnet-operation monitoring device disclosed in Patent Document 1, a turn-on coil to be energized when a movable core is turned on and a releasing coil to be energized when the core is opened, are wound around the outside of the movable core. At the time the turning-on operation is performed in such an electromagnet operation device, a current is caused to flow in the turn-on coil, so that the coil is excited and an induction voltage is generated in the non-energized releasing coil. According to the electromagnet-operation monitoring device, each value of the current flowing in the turn-on coil and each value of the induction voltage generated in the releasing coil are measured, and in their respective temporal waveforms, inflection points (the timing of the operation command, the timing of the start of the movement of the movable core, and the timing of the completion of the movement of the movable core) are detected, so that a necessitated time for the movement of the movable core is calculated. In the case of opening operation, each value of current when a current is caused to flow in the releasing coil and each value of the induction voltage generated in the turn-on coil are measured.